Cleaning installations for printing machines are known in the art. For example, U.S. Pat. No. 5,390,598 discloses a wiping device for an intaglio printing machine comprising a wiping cylinder and an installation for the continuous cleaning of said cylinder. The principle and basic technical features of the wiping device as disclosed in this patent are incorporated by reference to the present application. The installation comprises a container for receiving the cleaning liquid which continuously acts on the wiping cylinder and cleaning elements in contact with the periphery of the wiping cylinder comprising, in the direction of rotation of the cylinder, brushes and/or wiping blades and at least a row of nozzles parallel to the axis of the wiping cylinder, the nozzles being arranged to eject the cleaning liquid into the region of contact of the cleaning elements with the wiping cylinder. There may be one or several rows of spray nozzles, which send a cleaning solution under pressure. Known cleaning solutions are disclosed for example in U.S. Pat. No. 5,855,787 or in European patent application No. 0 927 632, the content of which is incorporated by reference in the present application.
U.S. Pat. No. 4,236,450 discloses another cleaning installation for the continuous cleaning of a wiping roller of a printing machine, the principles of which are incorporated by reference in the present application. This installation is characterized in that it comprises at least two rows of nozzles arranged parallel to the axis of the wiping roller, the nozzles spraying the cleaning solution onto the surface of the wiping cylinder. An example of a nozzle disclosed in this patent comprises a plate pressed against a wall of a support, said plate comprising small grooves in order to spray a continuous film of liquid. All the rows of nozzles are connected to pumps, which supplies them with cleaning liquid.
In another embodiment known in the art, the nozzles are made of a shaft of rectangular section comprising an inner channel parallel to the axis of the shaft, in which the wiping solution is sent under pressure, and an array of holes forming the nozzles, which are formed on the side of the shaft facing the wiping roller. Said holes are in communication with said channel in order for the solution to be sprayed against the wiping roller with a given pressure.
The problem encountered in the known installations is the fact that the nozzles, which have a small diameter, may be blocked or obturated by particles present in the cleaning solution so that the cleaning effect is reduced. In such case, it becomes necessary to stop the printing machine, remove the wiping cylinder to gain access to the shafts with the nozzles and to remove said shafts from the machine to be able to clean the nozzles in a remote place. Once this has been done, the shafts must be assembled and adjusted in the machine and then only can the wiping cylinder brought back in position. All these operations are time consuming and, since the machine is not working anymore, they have an important cost.